This particular answer can help you.
Manusmriti 3:5. A woman who is not of the six generations of the mother and of the father's gotra is recommended to twice-born men for wedlock and conjugal union.
If it was the cousin-brother, As your uncle already married in that family, that means your Gotra is different from her gotra, It should not be a problem.
Re-marriage is allowed in some circumstances.
If the women was virgin after the death of husband.
Manusmriti 9.176 “If she be (still) a virgin, or one who returned
(to her first husband) after leaving him, she is worthy to again
perform with her second (or first deserted) husband the (nuptial)
Baudhyan Dharma sutra 4:1:16. If, after ...