Wow this story paints an untraditional "family", connected by love and not blood.
Younger seme is "papa" to a little girl whose bio parents have both passed away. Her bio dad was a one-night stand client when the young seme was selling himself to pay for his late mother's medical bills, turns out, the man had little time left himself due to cancer.
Older uke is gay and has always regretted his orientation because he wants to give his old mother a "real" family. She does not mind though, because they are not related by blood either, this is just personal pressure that the uke puts on himself.
They basically come together to form a family of two men, a kid, and an old mother.
Ibitsuna Bokura no Katachi