The definition in Strong's Concordance for that word is "akin to, related; subst: fellow countryman, kinsman.". It's used multiple times in the NT, and it's rarely translated as "cousin" and more often translated as relative or kinsman. Even in the verse you cite, in most translations it is not translated as "cousin". Only about a fourth of the translations on Biblegateway.com render it as "cousin". Without knowing the parentage of those involved, is it as generic as "adelphos". And I provided a Septuagint example where based on the parentage the relationship is clearly a cousin, yet it is translated into Greek as "adelphos".
The most definitive and honest approach from a Scripture alone perspective is that there's not enough information to know the exact relationship of these people to Christ. That's a perfectly legitimate answer. To profess more than that leaps beyond the text of Scripture and tries to use words that have been proven to indicate only a relationship of some type, to now mean something specific that they in no way can be said to conclusively state. They're relatives. That's all we really know, from Scripture. To assert more is to go beyond what Scripture says.