My cousin says she had head lice. Are family members more likely to get the same thing?

Possibly. If you in deed have lice, or get it. It can be treated most of the time with an over the counter medication. (rid, permethrin). Apply one application, and reuse in 7 dys.
Human only pbm. Lice is a human only problem that thrives is confined spaces and close living situations.The lice often travel to a new host on scarves, combs, towels or directly thru close contact.10 d after hatching they are sexually mature & lay eggs at the hairline stuck to hair.A new crop of lice need to feed & feeding leads to scratching & greater chance to be cast off.Whole families are often infested.