My spouse and I frequently refer to one child or the other as "that's your kid", usually when exhibiting a trait characteristic of one parent in particular. Jo

My spouse and I frequently refer to one child or the other as "that's your kid", usually when exhibiting a trait characteristic of one parent in particular. John Adams may have been referring to a theoretical class of sons that may have included unborn future sons, which may or may not have been born to Abigail. He might have said to her that he wants his sons to share his values, just as he might suggest that her sons should share hers, and it would be coincidence that those two classes happen to be identical. Or he might have believed that all sons were intrinsically their father's children, not their mother's. It's a lot of implied meaning to derive from a possessive pronoun. I wouldn't make too much of it.