1. The said brothers have no legal right to claim such properrty which was documentarily funded by your Husband (which you would need to prove by documents of FIL Bank account).
2. Similarly said brother have no legal right to rent out your Title-Ownership property and it would amount to criminal trespass, intimidation, breach of trust, cheating, fraud.
3. You can file a Police FIR, requesting investigation and charge-sheet, for offences like cheating, intimidation, fraud, breach of trust etc.... against the person, supported with all relevant supporting documents.
4. IF the Police does not take action, THEN you can file private criminal case u/s 156(3) Cr.P.C., in the local Magistrates court, seeking directions to the Police to investigate and file charge sheet. The said Person may come down for settlement.