Im a new muslim convert, and before i converted i deposit a money in a commercial bank with interest, there is no islamic bank in my place can i use the interest in paying my relatives tuition fees for they are not capable of doing so.
Putting money in riba-based banks is a haraam action, and there is no concession allowing it except in cases of necessity; in such cases it should be limited to putting it into a current account without taking any interest on it. This has been discussed previously in the answer to questions number 104349, 23346, 49677.
The riba or interest that is received from putting money in the bank is riba which is haraam. Hence you have to get rid of it by spending it on various charitable causes. The owner of the money does not have the right to use it for his personal benefit or for the benefit of those on whom he is obliged to spend, such as his parents, children and wife.
But if your relatives are those on whom you are not obliged to spend, such as if they are your siblings or other relatives, there is nothing wrong with paying it on their behalf as fees to register them in school. There is also nothing wrong if you give this interest to them to spend it on their various needs, especially since they are poor and needy.
And Allah knows best.