IME, 14 months is far too young to do anything other than intervene, say firmly but respectfully "No hitting. Hitting hurts.", and redirect onto something else.
I think starting around age 2 we started with the natural consequences idea, which I think I actually got here on MDC in the Gentle Discipline forum. Basically, if one of them would hit or bite (etc.) the other one, I would say "No hitting. We do not hurt people." and instead of just 'here's a new toy to distract you', I would actually pick up the "offender" and remove him/her from the situation saying, "When you hit, you cannot play with us." and then put them (for 1-2 minutes here I'm talking) in the kitchen on the step there and make them sit there. This is NOT the same thing as a time out, which we don't do... this is simply the natural consequence for doing the most anti-social thing imaginable... harming someone else. If you have a booster seat or highchair with straps you could buckle them in there too, or get the Pack N Play back out and put it right outside the room where you spend most of your time. The idea is a very short confinement where they cannot just get up and run around having fun... again, not for the purpose of just randomly doling out time-outs but because when someone hits or bites, it is NOT okay and they must stop playing immediately.
This has worked remarkably well with us and is the approach we still use when tempers flare and someone starts being physically agressive like that. Now that they're 3, they talk so much more and understand much more abstract concepts, so when things have cooled off, we also talk about why hitting is wrong and other ways to solve problems, and role play how to ask for a toy or wait your turn or whatever. I also make a point of praising them when they ARE playing "nicely" together, saying something like "Boy we're having such a good time taking turns with the Sit N Spin" or "Isn't it fun to all play dollhouse together?" just to bring their attention to the fact that life IS a lot more fun when everyone cooperates and treats each other with respect.
Good luck. I know a lot of people, including myself who say the 15 months to 22 months stretch was BY FAR the hardest part of having twins, even harder than the newborn period in terms of exhaustion and feeling at the end of your rope. It really does get easier and that's not just something mamas of older twins say to blow smoke up y'all's you know what.