Recovery of my deceased daughter's marriage jewels&dowry; from in-laws

My daughter got married in 2008. As per Hindu tradition, I gifted diamond jewels, gold ornaments, silver utensils, house-hold articles, wooden furniture and cash dowry of INR 500000 for her marriage. My daughter met with an accident and died in 2014. After her death, we expected her in-laws and husband will give back to us the above-mentioned jewels, etc. and cash dowry. To our disappointment, they did not return my daughter’s jewels and cash dowry and they stopped talking to us and are distancing from us. My son-in-law is living in Australia and re-married now. He is intentionally avoiding us and stopped talking to us. The in-laws are living in Chennai. They are in possession of my daughter’s jewels etc and cash dowry. On approaching them with a request to give back my daughter’s jewels and cash dowry, they refused to return them. Please help us to back the jewels & dowry.