If you have your correct time and place of birth a chart calculation will determine which of the two signs you actually are. Your Sun can technically only be in one sign although it can absorb flavours from both.

My understanding of cuspal personalities is;
If your Sun is in the former sign (i.e. high degrees of the earlier sign) you will tend to have predominant characteristics of that sign earlier in your life and the mid to latter years tend to display more of the later sign. This could also have found its basis in solar progressions.
If your sun is low degrees of the later sign, although you will always have characteristics of both, you will predominantly be like the sign your sun is in.

I would be curious to know how other cuspal personalities feel about this as it is learnt theory and as I am not cuspal my self, so have not experienced that type of pull.

Muriel

Dear,
Sun is always seeing,Moon is always thinking,and Saturn is always doing,others are only supporting.No anyone in world know the way of Sun,in the light of Sun,everyone give give the suggestions, Where is going and what is the next step of Sun?nobody can predict.
Ramendra
Jaipur

Dear,
in Western Astrology, the sun is the main Character in play. Muriel