What if i dont do estate planning, will still my family gets benefits when i am die ?
Depends on what sorts of "benefits" you're talking about, who makes up your "family" at the time of your death, the laws of the state in which you live at the time of your death, and the laws governing whatever "benefits" you're talking about.
What if I dont have a wife and kids, where will be my asset goes?
If you die without a will, then assets that are part of your estate pass according to the intestate succession laws of the state in which you live at the time of your death. While intestate laws vary a bit from state to state, they all tend to follow a similar general pattern. If we assume that you die with no surviving spouse, no surviving children, and no assets that pass outside of your estate (e.g., because of a pay-on-death beneficiary designation on a bank account or 401k or things like that), then your assets would pass to your parents (if either are still living). If neither of your parents survive you, then your siblings and children of any deceased siblings would be next in line. If no siblings or children of deceased siblings survive you, then your grandparents would be next in line, followed by lineal descendants of your grandparents (other than your parents and their lineal descendants). In other words, your estate typically goes to group of relatives that is closest to you and which has at least one surviving member. Again, it varies from state to state.