Question:
Is it problematic if a divorced sister walks her brother down the wedding aisle since their mother cannot attend?
Answer:
The custom is that a married couple walk the chosson and kallah down to the chuppah, as a good siman. Therefore it should be a couple that walks them down. The divorced sister can walk in back of them, or there should be another couple walking down together with the father.
Best wishes
Sources:
Livushei Mordechai 3-22.
