In s4 and s5, there were no scenes of Shannon and Robby, which was disappointing. There were only scenes of Shannon and Johnny, and these scenes portray an important contrast between Shannon and Carmen.
When some of us point out that Carmen has never encouraged Johnny to try to build a relationship with Robby, people immediately bring up the school fight as a justification and frame Carmen as the sympathetic party. But, Carmen didn't try to encourage Johnny before the school fight either. In s2e5, when Johnny was drunk and told her about Daniel taking in his (Johnny's) son, she just focused on the rivalry and told Johnny to be the bigger person. In s2e9, Carmen herself told Johnny that Amanda said that Robby is going to go to school, but again she didn't encourage Johnny to try more to become a part of Robby's life. Carmen however throughout the series has wanted Johnny to do better with Miguel. She has blamed, explicitly or implicitly, Johnny whenever Miguel has been violent and been in fights---s1 Halloween fight, s1 avt, and s2 school fight---in which Miguel himself had chosen to behave that way. He picked the fight with Kyler on Halloween. He chose to fight dirty in the avt although Johnny even told him not to. Miguel also started the school fight between him and Robby and provoked Robby to his limit. Miguel was even going to break Robby's arm for no reason at all. He also used what Johnny had told him in confidence against Robby. Carmen has never once considered that her son is to blame. She is the mature adult and Robby is a kid who was attacked and antagonized by her son multiple times (including in s5). Carmen cannot be so self-righteous as to act like she and her son have the moral high ground in this situation. Also, she has willingly chosen to be in a relationship with Johnny who is Robby's father and to encourage Johnny to gradually take on more of father-figure role to Miguel since the school fight and now of course to the baby she and Johnny are going to have, regardless of Johnny's negative past and present behavior with Robby. She is the one who has chosen to intertwine their lives more. In s3e8, when Johnny talked about his failure with Robby and not wanting to fail with Miguel, Carmen talked about everything Johnny had done for Miguel and specifically told Johnny that he is a sensei and that is his calling. She is the one who later went to him and made the first move, and they slept together. In s4e4, she offered to get Johnny pills when he became impotent over Miguel hanging out with Daniel, changed the subject to telling Miguel about them, and then told Johnny in a motherly way that he can tell Miguel when he himself is ready because he said that kids can be weird about their mom's dating someone new (projecting his own past onto Miguel). She told Johnny it would make him feel better. In s4e7, she pressured him to play "dad" to Miguel and got annoyed with Johnny for botching it. In s5e1, she was aware that Johnny took Robby down to Mexico to look for Miguel. Miguel's father is a dangerous person so the whole situation was dangerous for Robby as well, but she was okay with Johnny risking Robby to get Miguel back. In s5e3, she did ask Johnny about how things were with Robby, but she didn't show more interest or encouragement that he do more with Robby than checking the status of their relationship, like encouraging Johnny to have breakfast with Robby instead of him having rushed over to have breakfast with them. Later, when it came to Johnny being a father to her kid with him, she scolded Johnny like a parent would and told him to figure out how to not be "that guy again" when they were buying the pregnancy test. He later gave her a speech that as long as he's doing this parent thing with her---their child---he'll do whatever it takes. She said that she knows he would. He then said that he may screw up from time to time, but he won't run away, and she then gave him the news that they're having a baby. In s5e5, she was only okay with Robby having dinner with them after Miguel said he was okay with it. Robby is Johnny's son! Why is Carmen in a relationship with Robby's father?
In s4e8, when Shannon showed up, Carmen immediately got territorial about Johnny. Shannon, recognizing Carmen's reaction to her, made her place in Johnny's life known: Robby's mom. Carmen kindly excused herself. Shannon then told Johnny to be Robby's dad and take care of the Silver situation. In s5e4, when Shannon came over to get Robby's things and she realized that Johnny had knocked up Carmen, Shannon was actually supportive and tried to help Johnny so that he wouldn't screw up again. While Carmen has never encouraged Johnny to do right by his first born from another woman but has steered his focus towards her own son who is not Johnny's, Shannon wanted to help Johnny not screw up with his upcoming child with another woman. Also, whereas Carmen simply scolded Johnny to figure out how not to be "that guy again", Shannon did something to help Johnny not be "that guy again". She gave him helpful advice and actually helped him set up a means to earn an income. (She also doesn't know that her coming over when she did saved him from being scammed, but that was just coincidence.) Back in s3, when Shannon was in rehab, she did to try tell Johnny that rehab would help him too. Carmen, despite being a nurse, has never encouraged or offered to help Johnny with overcoming his alcoholism and instead ignores it, even being fine with them celebrating their pregnancy at a club with Johnny ending the night drunk and commiting a crime. Oh, but in s4, she did offer to get him pills to help with his impotence because as a nurse she has access to certain medications. Carmen had shown more concern about Johnny's impotence than she ever has about his alcoholism.
The contrast between Shannon and Carmen is actually quite interesting and noticeable. Had Shannon and Johnny not been addicts/alcholics, it's likely they would have been more supportive of each other over the years. Shannon has always shown a rightful bitterness towards Johnny because he had abandoned her, in addition to abandoning Robby. Of course, Johnny and Shannon didn't have to actually be in a relationship to be supportive of each other while they co-parented Robby, but Johnny's and Shannon's poor decisions have lead to Robby's life and mental health being what it is. And, regardless, sadly they continue to emotionally neglect Robby, like not caring how the baby news would affect him, not caring who he wanted to spend the summer with, and not caring about the lifetime of trauma that they have given him because they were "young and dumb", as Shannon put it.
Seriously, though, go back and rewatch the Johnny impotence scene in s4e4. The level of dysfunction portrayed in Johnny and Carmen's relationship is as bad as Johnny's dysfunction in bed. Their scenes in s5e3 are also enlightening, as Carmen's annoyance of Johnny's stupidity and emotional immaturity is dripping in those scenes. I still can't believe that people cheer on this dysfunctional blended family built on Johnny neglecting and abusing Robby to prioritize Miguel and the Diazs, and Johnny having impotence over Miguel hanging out with Daniel while Johnny didn't care that Robby was training with Kreese. It's like "Come on, people! We, as an audience, can at least have better standards for healthy parenting and relationships." smh...
(These are general thoughts and not directed at anyone in particular.)
