When you are in any kind of relationship with the same sun sign, you will lack the quality and exalts. All positive personality and character of both will increase their intensity as well as negative traits.
You must make efforts to encourage good quality and minimize the bad qualities of each other.
But if the other planets in between the two horoscopes in particular month (month to show your inner feelings) and ascendants have a good relationship than a strong dedication, loyalty and respect will be there between you two. If the ascendants and the moon from the two horoscopes in the axis profitable than your relationships will be tense and difficult indeed.
So just check your compatibility with the sun just is not evidence of a pattern with the match making system. So better to get your horoscopes are eligible according to forecasters.