Friend not returning money borrowed

My friend (K) ran away from his house & against the wish of his family got married to a girl (S) who was 5 – 6 yrs elder to him. Since his family was against him & no one was there to help him, so I helped him in his marriage & since they needed funds I used to help them financially also. Now that they
are not getting along & have got seperated.

I had taken cash from my business to help my friend. And to show the entries in the book of accounts he had given me 2 cheques.

And since the amount is on a higher side around 70000/- I asked him to repay
the amount.

Now my friend is not ready to pay my money back does not answer my phone
I had sent sms to him, email to him but he does not reply.

So I send sms to his sister stating to repay my money. She says your money your friend had borrowed you take it from him only. And on the other side she does not allow her brother to pay my money also.

I have his two named, amount written & signed chq ( but date is not written )
( Amts written are 18000/- & 22000/-)

Can I write the date & deposit the chqs ?
In case they get dishonoured, can I serve him a notice ?
Still if they dont pay, can I file a case for recovery ?

And this 2 chq will take care of the 40000/- but what can remedies do I have for taking back the other 30000/- ?

Thanks