Does loyalty exist anymore?

I've been in three relationships in the past year which have ended with them cheating on me. I'm attentive, caring, intelligent, thoughtful, yet decisive and independent. I'm confident about my performance in relationships and have never gotten a complaint about anything. The only successful relationship (until we parted ways due to distance) I've had was with someone 9 years older than me and I've always been told to date someone older. My question is this; are most people in their late teens to early twenties (I'm 21 and just got out of a relationship with a girl who was 19.) too immature to hold a meaningful long-term relationship with someone who wants them to be happy as opposed to a 'bad-boy'?
Does loyalty exist anymore?
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