Nope, that's actually a thing. So, estrogen can cause the development of breast tissue in either sex. This is not the same as being so fat you have something kinda like boobs, but like, actual C cups on a skinny transwoman can be a result of hormones (might be surgery. but can be hormones. legitimately).

But this is because both males, and females, have breasts in humans. Like, the actual size/shape of them is different but the anatomy is largely there. Theoretically (and very theoretically I dont think anyone has proven this) you could get a male to lactate (at least, according to a biologist I was speaking to and it wasn't about trans issues at all) but it would be a really far from natural state. That part of sexual development is hormonally controlled and doesn't require different anatomy.