Q. I am single now, but I was married so I am not Kohein eligible. However, I recently met a Kohein who is not observant. I was wondering, wouldn't Hashem prefer that he get married and lose his Kohein status rather than stay unmarried, especially if he becomes more observant in the process?
A. As we know one born as a Cohen, cannot renounce to the status he was born with, and will be restricted during his lifetime to all normally applicable Cohanic prohibitions.
However, it is not uncommon in our days that people who are estranged from keeping the Torah, especially if that goes back also to parents and grandparents, may not be anymore considered Cohanim in Halacha, since one of the parents, could have been involved in prohibited relations that would turn him into a 'Chollol' or removed from the Kehuna.
A competent Rabbi should be consulted to investigate the history of his family.
Horav Shlomo Miller’s Shlit’a opinion is similar.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit'a