This is completely just my own opinion with nothing to support or deny it either way, but I would hypothesize that for Philip the idea of defection had at least come up in some corner of his mind. Like for Elizabeth, it's the absolute last thing she'd consider, but Philip is so much of a pragmatist, that I would have a hard time buying it completely came out of left field and he'd never thought about what could happen to the kids if they were captured. I don't think he hated the spy life, but I think he was well aware of the risks and the more attached they became to Henry and Paige, and also the older and more world-wise they got, the more that would have to play into his thoughts. And I think it does in Elizabeth's too, but she's so good at blocking out and shutting down things she doesn't want to think about, and he is more pragmatic.

And the same with Elizabeth and her feelings towards family/Philip. It doesn't make sense to me that it came completely out of the blue and one act of killing Timoshev caused such strong feelings to form, but rather that some basis for those feelings had been there and kept in compartments up until the point that their interaction in the garage shook everything up. It could appear that she was ice cold in the pilot, then all cuddly towards the kids in the second episode, but then I think that had more to do with stress of Timoshev because the kids don't really seem fazed. Paige says, "I love you too, mom," in a "duh" voice, not a "OMG mom is saying she loves me" voice. And I also think things with Gregory weren't just perfect one second, and then she dumped him in an instant for Philip, but rather that she'd probably recognized at some point along the way that things had become more complicated and she wasn't really the same person she was at 24, causing that connection to be not quite as blazing as it had been when they'd first met.