Scriptures mention that bachelors should not take part in shraddha rituals. However, in practice, they are allowed to participate in the Vishnu sthanam, and sometimes, due to circumstances, even in the Vishvedevar sthanam. But they should not take part in the pitru sthanam.
Men whose parents are still alive can definitely participate in shraddha. In fact, it is a common practice to include them in the pitru sthanam, and their participation is considered special.