The step home
"Living with a spouse's child or a spouse's relative".
src 
src
Most marriages do experience a case or situation where the husband or the wife already had a child (or children in the past). Some of which may be a mistake or unintentional before the couples met. This shouldn't be taken against anyone of them since they both aware of it. This may not be an ideal situation. The children in the house are not staying with their real father or mother. Expect some challenges because you have to love a stranger. It may not be easy but it may be worth it. Recognise that the fatherless or motherless have a special place in God's heart and he has said that he will personally fight those who oppress them.
Ye shall not afflict any widow, or fatherless child. And my wrath shy wax hot, and I will kill you with the sword, and your wives shall be widows, and your children fatherless. Exodus 22 verse 22, 24
... Thou art the helper of the fatherless.? To judge the fatherless and the oppressed, that the man of the earth/ may no more oppress. Psalm 10:14, 18
src 
src
You married your spouse with the background, accept it. You must love them unconditionally (Agape) without expecting a reward.
Recognise that the son or daughter is closely related to your spouse and that he or she loves him/her. Consider Abraham's mood when he had to send Hagar and Ishmael away.
And Sarah saw the son of Hagar the Egyptian, which she had born unto Abraham, mocking. Wherefore she said unto Abraham, cast out this bondwoman and her son: for the son of this bondwoman shall not be heir with my son, even with Isaac. And the thing was very grievous in Abraham's sight because of his son. Genesis 21:9-11.
Decide on the involvement of the child's other parent before you marry. Minimum interference in your new home is advised. Frequent interaction between the child's parents is not necessary. If possible, get a neutral person to act as a liaison to avoid questions and mistrust. Always endeavour to be a united couple in the eyes of the child. Know the reality of a bitter stepchild.
And Sarah saw the son of Hagar the Egyptian, which she had born unto Abraham, mocking. Genesis 21:9
src 
src
Believe God to fight certain battle for you. Seek counsel when necessary. Do not encourage or fan any rift between your spouse and the stepchild. Do not be seen to form a clique with your spouse's stepchild. Accept the fact that children are not perfect creatures. Your own children may also be stubborn or full of mistakes. A stepchild needs working on too. Handle him/her with love. Do not alway take your spouse's correction of the stepchild as hatred. Allow your spouse to train the stepchild in accordance with the biblical principles.
Nice advice to us, the fathers of tomorrow
Lol.. Of course we are.