I have not. I have heard of Alice Hathaway Lee Roosevelt, his first wife, and Edith Roosevelt, his second, but I can find absolutely nothing about the existence of this third wife, Eleanor...
The question then becomes "Why is this damn baby so important that it needs to restrict the player's freedom?"
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Personally, I'm torn on this. On the one hand, Bethesda has the right to make the game they want to make, and that includes making a character you play as the character they want you to play as. Age, race, personality, looks, gender, religion, all of that can totally be dictated by Bethesda if they want to, and if they feel it better serves the story they want to tell, then they should probably do it.
That said.
I do think it's counter intuitive for a company like Bethesda, which uses its character creation as a selling point for their games, to not be as inclusive as they can. If the name of the game is make the character you want, it seems odd that sixual orientation is the thing that gets determined for you. And I don't see why people are bothered by the fact that this is an issue for some people. Going "It doesn't bother me so it doesn't shouldn't be an issue to you" just comes off as petty and childish, not to mention unable/unwilling to actually discuss the issue with the people who care about it.
I'm straight, but I've played as gay characters of both genders in the past, and I wouldn't have a problem with a game "forcing" me to play as a gay character because it serves the game's narrative, just like I don't mind having to play as a member of this couple if it serves the game's narrative.
For me, the question is less "Why can't I play a gay man or a lisbian from the start," but "Why do we have to be a married parent?" I'm not bothered by it. In fact, I'm definitely going to be playing as a woman first because the female Sole Survivor strikes me as inherently more interesting than the male one (not to mention her voice acting doesn't sound like a robot). But my question is what purpose do the spouse and baby serve? Are they just something to emotionally manipulate the player and make the character sad at the beginning because they died? If so, why not play as the child, or start the game at your sibling's wedding, with the nuptial bliss being interrupted by atomic warfare and everybody you know and love dying? If it has to be your child because the kid is going to be the antagonist in the end like some people are suspecting... That's a really lame twist.
As a writer, I'm less interested in the restrictions that Bethesda's placed on the player and more interested in what purpose those restrictions serve.