It's certainly possible but you might find that you've lowered the signal strength too much at each location for reliable reception. If so, you'll need to add a signal amplifier into the setup.
Try it without an amplifier first though:
Buy a pack of coaxial plugs:
https://www.screwfix.com/p/philex-coaxial-plug-pack-of-10/18564
Buy some coaxial cable to form the new downleads:
https://www.screwfix.com/p/nexans-rg6-coaxial-cable-25m-black/195fk
Buy a 3-way splitter:
Amazon.com User Recommendation
Cut the lead in the loft where you want the join to be. Trim the end of the cable and fit coax plugs to them. (It's a straightforward task but there are Youtube videos to help you if needed). Plug the aerial cable into the input of the splitter and the lead going to your telly into one of the output sockets. (That should restore your telly reception on the main TV). Then cut two lengths of cable to feed to the other two sets and fit coax plugs onto each end of them. Plug those into the remaining sockets on the splitter unit and connect the other ends to the bedroom TV sets.