LISA - "and if you keep my commandents and endure to the end you shall have eternal life,which gift is the greatest of all the gifts of God." (D&C 14:7)
I am the only member in my family and no one else accpeted the gosple. So I understand they probably wont be in the spirit world. So how could I have eternal life?

JOEL - First of all, everyone who obtains a body and then dies will be in the Spirit World(including your family)(Alma 40:11).
They will be divided however into Paradise, where the righteous go, and Spirit Prison, where the wicked go and those who never received a fair opportunity to accept the gospel during life(Luke 16:22-26). Here they will be taught the gospel(1 Pet. 3:18-20, 4:6) and if they accept it and their ordinances are performed for them in our temples, they too can be exalted in heaven after the judgement. You may even be the one who teaches your own family the gospel in the spirit world(D&C 138:27-32).

Although we must do all we can to help our family and ancestors hear and accept the gospel, their salvation is ultimately up to them; and what they do does not determine our own individual salvation. What is required of each of us personally to obtain eternal life, is to live the gospel, keep the commandments, endure to the end, repent of our sins, and be married(sealed) to someone in the temple(D&C 14:7, D&C 132:19). If we don't have the opportunity in this life to be sealed to someone, God will see to it that it will happen in the next life. If we have done all we can to perfect ourselves, God will not deny us eternal life.