Got help from a nice lady who got me started on the right track with the right names. Confirmed the info on Royal websites and German websites. Some only in German but a friend who knows German was able to tell me what they said.
Friedrick Wiliam, "'the Great Elector" and his 2nd wife
Princess Dorothea of Schleswig-Holstein's 3rd son;
Duke Albrecht Friedrich von Brandenburg-Schwedt
b-1/24/1672 (he was the half brother of King Fredrich 1 of Prusia
and the uncle to Fredrich the Great)
Married Princess Marie Dorothea of Kurland in 1700
they had 3 children;
Fredrich Wilhelm von Brandenburg-Schwedt
Karl von Brandenburg-Schwedt
Markgraefin Abertine (only daughter)
the 1st son Fredrich was born in 1701 and died 1741 in
Battle of Mollwitz
His children;
Alexander Heinrich (henry) b-1721 d-July 1793
Solomon b-8/24/1722 d-March 1786
Wilhelm Heinrich also b-8/24/1722 d- March 24, 1796 in Freedrick,MD
Johannes John Martin

Wilhelm Heinrich von Brandenburg-Schwedt marrieda Ann
in Holland in 1747
children;
Maria
Elizabeth
Heinrich (Henry)
Johann (John)
Wilhelm (William)
Arron
Eve
Jacob
Matthias
It looks as if it was Wilhelm Heinrich and histwin brother
Solomon who went to Holland. Wilhelm married in Holland
but returned to Prussia were his children were born.
Records show Mathias was named Elector of Estates in 1758
Records also state that a return to Catholic was not in the time of
Fredrich the Great, because he didn't believe in any God.
Two places showed that Matthias came to America with his father & uncle. Other sibs came later.
Court records show that Mathias' father Wilhelm did died in
1796 in Freedrick,MD