I look at male and female in the medical sense, as referring to body and chemical structure as sex defined characteristics and man and woman as gender definition. Does being pregnant make you less of a man? Well no. There are dudes, though extremely few, who say they would do it if poss...and even fewer actually would if it was possible. But it is, by definition, the most feminine thing someone could do. Only a female body can get pregnant. By definition, medically speaking, this is truth. So saying being pregnant doesn't make you less male, is false. It makes you the exact polar opposite of male, which is why so many transguys have a problem with it. Being pregnant is only possible in a female body with way more female hormones than a regular female. I personally can't wrap my head around why any transguy would want it. I know we're all different but personally I understand a CIS-man considering the idea more understandable than a transguy, for cis-men are thinking of the unknown while transguys know what it is to live in a female body. If they're dysphoric enough like that, why amplify it?
The brother option sounds like the best bet in my opinion, better for you and baby. You can't be on T and pregnant so going on t would be delayed, and if you have top surgery you wouldn't be able to breast feed which is always best for the baby when possible.
It also could send the wrong message to the already present daughter that you are so desperate to have a kid that's part you, like they're not good enough for your love because you're not the real dad.
Family is nothing to do with blood and that should be an absolute last connection factor in my opinion. I live thousands of miles away from unaccepting blood related family. I now have surrogate parents who are more family to me than anyone blood related.
I also hate Thomas Beattie. If you wanna be a pregnant transguy, go ahead and do it in private. But trying to be some unwanted advocate for pregnant tranguys all over TV and magazines wasn't asked for and it sure as hell didn't help us.