Question: If a house is jointly owned by 4 people, and they all use it as principal residence, do each one get 250,000 tax exemption?

Answer: As long as each unmarried co-owner satisfies the two-out-of-five-year ownership and use tests, each gets to exclude up to $250,000 of his or her share of the gain from the sale. (Married couples who file jointly can exclude up to $500,000 of their gain).

From the IRS at: https://www.irs.gov/pub/irs-pdf/p523.pdf