What's a nice way to ask "How many baby mamas are there?"

I went on a date with a guy I met online and we had a great time. He's super fun to be around. He has several tattoos and his arm has Zodiac signs with a letter by each. He said he has a tattoo of each of his kids Zodiac signs with their Initials.... There were seven of those tattoos. At first I thought it was 5 but he unfolded his arm and said he has 7 kiddos. I obviously don't want to assume he has multiple baby mamas because some people do genuinely just have a shit tone of kids with one person. But I would like to know and idk how to ask without it coming off as rude.