Qualifying Relative

Disrupted adoption. Had foster son for 157 days. Son was ward of the state for 89 days and placed with his sister for 119 days. Not sure if residential treatment occurred before or after placement with his sister. We were fortunate to adopt our other son.

I was wondering if we can be a qualifying relative or if it’s likely the sister can claim him as a qualifying child. Is there a penalty that can be assessed or can we lose the ability to claim the child tax credit for our other son if we attempted to claim our former foster son? I think TurboTax is wrong that we can claim our foster son

If I don’t claim him as our foster son, I simply add $2,000 to the adoption credit we take this year