 If you liked
Katekyou Hitman Reborn!
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 ...then you might like
Fate/Zero
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Both have people with magic/powers that could lead to disasters
They both have some kind of 'family' blood line (Vongola has the vongola blood line, magician blood etc)
Fate/Zero has more 'pairing' relationships, whereas Hitman Reborn has a lot more grouping.
Fate/Zero has 'Classes' and Hitman Reborn has 'Flames'
Overall, they're both great series, noting that Fate/Zero has a bit darker side to it.
(Personal opinion: All their openings and ending songs are really great)