Really. If anything I'd say the loss of a child you had just begun to build bridges with might be even more devastating than the loss of one you'd known your entire life.
Hell, if you don't think Kirk's devastated by David's death, I recommend rewatching the scene in TSFS. One of Shatner's better performances IMO.
I usually limit my viewings on SFS because I dislike so much about it, which is a shame because it starts off pretty well. I find Shatner's response to David's death to be a low point in the series, down there with Stewart's, "the line must be snorted HERE!" in FC and his bawling in SAREK. Compare any of those with Shatner's response to Edith Keeler's death or even his humbled/subdued end scene in REQUIEM ("an old and lonely man and a young and lonely man - we put on a pretty poor show, didn't we?") and ... well, there is no comparison.
The SFS scene is horrendously staged for one; if Kirk is going to fall, it should be after SEEING David killed, via one of those convenient 'shows everything' main viewscreen visuals, instead of getting the news as a phone call. You could have racked focus off screen,staying on Kirk's back, and seen him slip down out of frame, diminished by what he had seen. Unless you're really really good, it's often best to be shooting an emotional reaction obliquely, because otherwise it can just read like making faces, something Shatner often is accused of anyway. Now if you're Mandy Patimkin in CHICAGO HOPE and reacting to an attorney-friend who has just died on your operating table, you CAN pull it off, but that is more the exception to the rule.
I'm not picking on Shatner at all; his work in the scene with Morrow in the lounge is excellent, as is his early scene with Bones in Spock's quarters, but I think Nimoy made a lot of mistakes, many of which compounded Bennett's, and the result is for me the definitive TOS feature misfire, the most squandered of opportunities.
In answer to the other question, I do not have children, nor have I ever wanted any (if I were well-off I would certainly have adopted, as there are more than enough children in the world needing parents, but I'm not & that's that; even if there weren't a surplus of children in such a jam, I haven't ever felt the need to help conceive one that would likely be color-blind, nearsighted & diabetic.)
I have no contact with any family members (not counting my wife, as that is a choice, not something that happened as a result of nature), as none of them are sufficiently well-behaved or possessing enough integrity to merit my concern. I DO have a few friends (many have fallen by the wayside because they didn't live up to the standards I maintain for friendship, and in one instance where I feel I didn't measure up) who I would risk job and/or life for, because THEY are my family.
Yeah, I absolutely LOVE tff.