There seem to be conflicting accounts of whether Michal, daughter of Saul, ever had children. Here's 2 Samuel 6:23:
And here's 2 Samuel 21:8:
The reason I have to use the King James Version for these quotations is that most modern Bibles are united in declaring this to be a scribal error, and that the original manuscript probably referred not to Michal, but to her sister Merab. Even the NRSV, which does not normally make any effort to cover up contradictions, gives the following:
The notes to the NRSV base this on two Hebrew manuscripts and the Syriac translation, though the Masoretic text reads Michal.
Another factor in favour of this argument is that Michal was not married to Adriel; her sister Merab was. So it makes a lot of sense that these should be Merab's children. I think it is likely that the modern Bibles are correct.