They're brown. Is it lice or could it be something more serious!?

Nits. Nits are louse eggs. Nits can be white, yellow, tan to gray depending on if the nit has hatched, if it is dead or what stage of development it is in. After hatching the shell may be wrinkled and yellow or white. Nits adhere to hairs, unlike dandruff.
What is brown? Where are "they" and what do they look like? Could be lice but really can't tell from your question.