
I’m not sure if I agree with that. Sinclair would obviously care more about Martin and see the kids as inconvenient distractions, but Martin seems like he would care a lot more than he is depicted to. He was so devastated by the loss of his OG baby that he literally went catatonic.
He didn’t even want a kid at that point, so even if the timeline was different I feel like he would at least show his kids an average degree of affection and consideration

Martin does show an above average level of care for the 3 boys. If he didn't, he would have left Sinclair to raise them as he liked instead of interfering.
But in the same Sinclair views Martin as a priority, Martin also view Sinclair as his number 1. Which is why in my opinion his grief over the initial loss of his pregnancy was not because he lost the child, but because he lost his and Sinclair's child.

I said AVERAGE, not subpar. Martin stepping in to prevent abuse, neglect, or dehumanizing behavior towards his kids doesn’t make him a good, or even average parent in terms of affection. It’s the bare minimum to not be considered a shitty parent.
Going by your logic, he was so devastated at the loss of their child (at a point in time when he had never wanted kids and spent most of his life trying not to get pregnant) that he literally went into a non responsive catatonic state. This version probably had a lot less trauma and clearly wanted kids enough to get pregnant more than once (I’m pretty sure the daughter was born separately from their sons).
I guess it’s true that Martin never had healthy parental figures to model how to treat his kids, but this situation is so bad that it’s more of a basic social issue than parenting specific. Martin has been shown to have at least average social skills, so the idea that he can say shit like that without understanding how weird and upsetting it would be for the other person…is kind of nonsensical.

I am reading between the lines. All of the kids really love Martin and feels strong desire to be close to him, but there are definitely some glaring issues in how they were raised as kids and treated now.
Sinclair is obviously an emotionally distant, cold, and jealous parent to the boys, so it’s not surprising that they would be more dependent and closer to Martin. I suppose on a financial level they would be considered average parents because they provided, food clothes, shelter, and material support until the day they turned 18 after which they lost average status since they kicked out their kids for no reason.
On an emotional level, they are both subpar parents. Sinclair’s coldness, jealousy, and lack of interest would do a lot of harm to a developing child. The reason they favor Martin so much is only because he is so much better IN COMPARISON.
If Sinclair was a normal parent in terms of warmth and emotional support, they would have issues with Martin for all the callous comparison that make them feel unappreciated and never good enough. The reason they think Martin is a saint is because he is compared to Sinclair, and they have no way of knowing the way he treats them isn’t fair or normal without experiencing healthy family dynamics.
Just because the kids love him doesn’t mean he was a good parent. This is the kind of scenario that subtly messes a child up until they finally notice in adulthood, go to therapy to deal with it, and go low contact with their parents.
I kind of dislike how MC and Sinclair’s relationship is being depicted as so intense and all consuming that their children are neglected and mistreated. Just rubs me the wrong way. Apparently Sinclair treats the kids as competition, and MC is really insensitive in how he compares them. They mentioned that they were essentially chucked out of the house by Sinclair as soon as they became adults and Martin was just ok with that. It seems like all of the kids really adore Martin and try to make loving gestures towards him, to which he just compares whatever it is to a better version that Sinclair did/made/bought.
They’re not depicted as having trauma, but it would be absolutely brutal to have every gift, favor, and surprise made towards someone you love constantly degraded by that person. Even if your spouse got you a better and more expensive watch, you don’t have to say that to your kid right as they’re giving you something they picked out for you. The entire dynamic is way off.