Lets see... similarities:
1. they are both combat airplanes
2. they both have 2 engines
3. they both have two vertical tails
4. they both have stealth characteristics
Yeah, they must be twins, right?
dis-similarities:
1. one is conventional wing-tailplane while the other is canarded semi-delta
2. one has full stealth configuration while the other has
"frontal-aspect-only" stealth
3. one has box-type pitch-only thrust-vectoring nozzles while the other has round nozzles with Russian-designed all-angle thrust vectoring to be added later
4. one has forward-swept vertical tails, the other aft-swept
5. one has close-spaced engines, the other has wide-spaced engines
Shall we continue?