If woman(F) have sex with man(M1) to have son(Ma). And woman(F) have sex with man(M1)'s brother(M2) to have daughter(Fa). Daughter(Fa) have sex with uncle(M1) to have son(Mx). That's nasty insect. Anyway, here is listing that I could think of that way...

F/M1 = Mistress/1st Master
F/M2 = Mistress/2nd Master
F/Ma = Mom/Son
F/Fa = Mom/Daughter
F/Mx = (Grandma/Grandson)/(Aunt/Nephew)
M1/M2 = Brother
M1/Ma = Father/1st Son
M1/Fa = .75 Uncle/.75 Niece
M1/Mx = Father/2nd Son
M2/Fa = Father/Daughter
M2/Mx = (Grandpa/Grandson)/(.75 Uncle / .75 Nephew)
Ma/Fa = .75 Sibling
Ma/Mx = .75 Sibling/(.75 Uncle/.75 Nephew)

"3/4" is too confuse, so I replace it as ".75".

Otherwise, I never met anyone who have 3/4 sibling. Hey Philip Fry is grandma himself! Mind blow!