Deduction u/s 24b - Interest on loan

Yes, possible if the payment receipts issued by bank are in all three names, jointly.

Also, have purchased the house from second seller and the building is still under construction, can we claim in the same year?

Also, in agreement the ratio of ownership is not mentioned
Further, the home is taken in all the three members name so while taken deduction we have to divide interest in the ratio of ownership?

1. No. Not allowed over under constriction property, till its completed.

2. Not mandatory.