During the years 1675 to 1678 was there a reason a family in france would uproot to Germany? One generation later changing name from Herlan to Erlewine ?
That's a very specific time frame and example. I guess you are asking because of your family history?
They were most likely Huguenot, french prostestants of the calvinistic school. They were oppressed in France, which led to the French Religion wars. The St. Bartholomew's massacre was a central event during those wars. This religous turmoil was ended with the Edict of Nantes from 1598, in which Henry IV promised religous freedom to the Huguenots and protection from state persecution. They were allowed to pratice their faith and keep schools and churches, but a large part of the catholic population and of course the clergy were hostile towards them.
At the end of the 16th century, many french protestants started to leave France, mostly towards the German countries, the Netherlands, Suisse, England and America. The first arrived in Germany around 1597. In the Holy Roman Empire the statute of Cuius regio, eius religio was instituted with the Augsburg Settlement, which meant the faith of the ruler of a region is the faith of this region. Everyone else who lived there could leave (Which was not self-evident for a subject to move somewere else at that time). So the Huguenots could come to protestant German principalities without fearing oppression. They were even welcomed, because most of them were part of the "middle-class" (don't know a more time appropriate expression), pious, hard-working people and well educated.
In 1685 the edict of Nantes was reversed by the edict of Fontainbleau, signed by Louis XIV., which forbid Protestantism in France completely. The churches of the Huguenots were closed, they were not allowed to practice their rites and most important of all, they were not protected from persecution anymore. Friedrich Wilhelm Prince Elector of Brandenburg and Duke of Prussia, known as "the Great Elector" and a calvinistic Protestant himself, issued the edict of Potsdam in the same year, which guaranteed the Huguenots not only religious freedom, but also privileges like tax reliefs and subsidies for busineses. Of the 50.000 french protestants arriving around 1680 - 1685 in Germany 20.000 settled in Brandenburg-Prussia, which was not the Kingdom of Prussia yet. Berlin grew substantially through to the new immigrants. Brandenburg, like many other German regions, was still ravaged and depopulated by the 30 years war, every hand was needed, especially well educated and determined ones.
Without more specific details about the family of Erlan / Erlewine it's hard to tell the exact circumstances of your case. Before the edict of Fontainbleau of 1685, the attidude against Huguenots in France grew more and more hostile over the years. For example Madame de Maintenon, Louis' "secret" second wife and prior to that (early 1680s) already a very influential person at court, spoke in favour for the persecution of Protestants. She was known to have a huge influence on the King. In her later years it was said, she was the second most powerful person in France. The edict didn't hit the french Protestant community by surprise.
Many Huguenot families did very well in Germany, especially in Prussia. Some of them localized their name or it was localized over time by pronounciation. Their communities thrived and they rose to influential positions. They also spiked the intelectual life. Many french idioms can be found in modern German and in many dialects. One of the most famous Huguenot families to this date is the family De Maiziere. One of them (Thomas) is the Minister of the Interior right now, his elder cousin (Lothar) was the last Prime Minister of the GDR until the re-unification. Thomas's dad was a general in the Wehrmacht and the Bundeswehr.
My source is a German book, unfortunatly I can't cite or have read any english language books about this subject.
Rudolf von Thadden: "Die Hugenotten 1685 - 1985", 1993.
Edit Forgot something: It depends from where the family Erlan immigrated and where they settled in the end in Germany. Not all Huguenots went to Brandenburg and not all were that gladly welcome upon arrival. The changing of the name from french to a more germanic sounding name may have been a process over time or it may have been a precaution to integrate faster into the new community. But again: More details are needed.