Paternity Mystery

I’m married with two sons. My older brother married after me in his late thirties to a girl in her twenties. Several years after he married, my brother confided in me that nothing was happening despite trying for a family.

A few years later, my sister-in-law came to me while I was fixing her laptop, and we had a brief affair, which I’ve always regretted. The upshot is that she became pregnant and had a daughter who looks like me, although my brother and I share similar looks.

I’m sure my SIL used me to get pregnant; if that’s the case, I feel better about betraying my brother. The thing is, I would love to know if her daughter is mine.