Hull City have signed Brighton & Hove Albion full-back James Furlong and Aston Villa winger Jaden Philogene for undisclosed fees on three-year deals.
Philogene, also 21, has had previous loan spells in the Championship with Stoke and Cardiff.
The Tigers have not said if either player will be available for Saturday's trip to Leicester.
Find all the latest football transfers on our dedicated page.