I think they are not the same.
The F650 (Funduro, Strada, ST etc.) 1993-2000 was an Aprillia design, the only major difference being BMW bought a 4 valve 2 spark Rotax rather than the 5 valve 1 spark. Nearly every service part was the same.
In 2000 BMW cut all ties with Aprillia to avoid paying for the design work they did, started manufacture and design in house and introduced FI, ABS etc. F650 GS, CS and Dakar are totally BMW except for the Rotax engine.
My thought that the Pegaso does not have the same forks would also (I think) tie up because Aprillia did not offer ABS and so don't have holes for the sensors? If this is correct some internal parts might be the same but the fork lowers are different.
A picture would show this easily.