There isn't any contradiction between Christianity and evolution. Anybody reading Genesis as literature (i.e. without committment to a particular belief about it) would immediately recognize that the Adam and Eve story and the Flood story (as well as some others) are fables with a moral message, not intended as historical records. The understanding that they are not to be taken as literal history goes back at least to Augustine.
If God is omnipotent, then it was within his power to use evolution as part of his creation plan.
You might remind your family members of the evangelical principle "sola scriptura". Only the scripture itself is authoritative. A Christian is not expected to take what his preacher says as authoritative, but to question it. And you are entitled to come to your own understanding of how to understand scripture.
You might find
this web page to be useful.
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