Her younger paternal uncle acted as her guardian for her marriage, even though the older uncle was there
Question

There is a woman who is a virgin, and does not have a father or brothers, but she has paternal uncles. A man proposed marriage to her, so her younger paternal uncle acted as her guardian for her marriage, even though the older uncle was there. Is this marriage valid?
Praise be to Allah.If the matter is as you describe, that she has no father or brothers, then if she has no nephews, her younger paternal uncle acting as her guardian for her marriage is valid, even if her older paternal uncle is there, if her younger paternal uncle is an adult of sound mind and good character, and he gives her in marriage to a compatible man with her consent. That is because if the guardians are equal in terms of degree of closeness to the woman, it is valid for any of them to act as her guardian for her marriage, and giving precedence to the oldest one is merely recommended (mustahabb). And Allah is the source of strength. End quote.
Shaykh Muhammad ibn Ibrahim Al ash-Shaykh (may Allah have mercy on him).
Fatawa al-Shaykh Muhammad ibn Ibrahim (10/112)