Complicated situation,

My sister had a one night stand two days before her period, it was protected sex(June 10). (Still single at the time) got her period June 12...

A couple days later the guy she had been getting to know for the past 4 months asked to be official bf and gf. They had not been sexually active prior to this. On June 18 they had unprotected sex (he was tested for stds and so was she, he was medically told it would be impossible for him to have kids) since the doctors had told him that he would never be able to have kids they had unprotected sex given bothe were clean from any stds and all that.

On the24 my sister started her fertile week and she also had unprotected sex the 25th.

She took a test today July 20 due to her period being late. Period was due July 9th.

She got a positive digital test.

So now I have a feeling her baby daddy could potentially be her one night stand but she said she was careful and she knows he didn’t cum inside her (they used protection) neither of them were drink or anything so she knows it was protected. But then idk cause her boyfriend was told that he couldn’t have kids. My sisters met his parents and they talked on the subject before so she knows he’s not lying about that. Everyone in his family knows that doctors told him he couldn’t have kids. He has major sperm issues (previous relationship he was in they tried for7 years he got tested that’s how he knows) but he i know sometimes God has other plans so I don’t know what to think. Her boyfriend is the sweetest guy we all met him and I hope it’s his baby.

Anyone else what do you guys think?