I strongly suspect that the woman is a servant, not a relative.
In addition to the clothing and the body language, which looks subservient to me: there's only one place set. She's not going to be eating with him, she's just waiting on him. Wouldn't his mother, aunt, grandmother etc. be sitting down and eating with him?
As she's talking about family relationships, however, she's probably not just a random maid hired last week. She may be the family nanny, or something of the sort.