What should I do if semen gets on my bed while I'm asleep, especially if I can't wash it in front of my family, or if I'm sleeping at relatives' and feel shy about asking to perform ghusl?

Washing bedding from semen is not obligatory, because semen is pure according to the most authoritative opinion. It is, however, recommended to wash it for cleanliness if it is wet, or to rub it off if it is dry. If it is left, there is no blame on the doer. As for performing ghusl (ritual bath) due to semen or sexual intercourse, it is a religious obligation, and one must hasten to do so without embarrassment, for the Companions did not shy away from such matters.