While you may be thrilled to have a close relationship with your stepchild, there are some things that you will need to think about, and deal with.
You are not the biological parent, and you never will be. Even if the child prefers you to their natural parent, the important ties of blood & genetics are simply not there. Unless you are willing and able to adopt the child, you have no legal rights where they are concerned. One of the pitfalls of being a step parent, is that you are expected by society, to love, nurture, and help raise a child that you have no legal rights to. They can be taken from your life in the blink of an eye, and there is little you can do to fight it.
Speak to your spouse about limitations and boundaries they may feel you should observe. In most cases, the biological spouse is ecstatic that you are growing closer to their children, and that you are more than happy to take on the responsibilities. However, there are biological parents whose ideas of proper guidelines entail you keeping a distance from their child.
It is recommended that children are not encouraged to or be allowed to call the step parent “Mom” or “Dad”. While you may be more of a Mom or Dad to them than their absent biological parent, this is a volatile area that needs to be approached with caution. It is far better to have the child call you by your first name, or possibly a nickname they choose for you. The title of Mom or Dad should be strictly reserved for the biological parent.
Embrace the growing relationship with your step child, but never attempt to “replace” the missing biological parent. That role, for better or worse, does not belong to you. All children need to be able to identify the main characters in their lives without the added confusion of having the lines blurred. This is essential to their emotional well being as they grow into adulthood.
Most importantly, when your step child is bonded to you, enjoy! Take advantage of the opportunity to have another loved on in your life.