I’m on the brink of a sexual relationship with my sister

DEAR DEIDRE: MY sister and I have shared a passionate kiss and are on the brink of a full sexual relationship. 

Growing up we thought we were half siblings, but last year we discovered my step-mum had cheated on my dad and my ‘half-sister’ is not related to me at all. 

Since finding out the truth, I’ve started to feel differently towards her and found myself attracted to her - even imagining us together.

I’m a man of 39 and my mum passed away when I was a toddler. Dad remarried when I was six years old and I loved having a new mum.

When they had a daughter together one year later I was so excited. I adored her and as we grew up, we became best friends.

Sadly Dad’s marriage broke down after 10 years but my ‘sister’ and I remained very close. I’ve always recognised that she is pretty and as an adult - very attractive. She’s 32 now.

But things have definitely developed since learning she isn’t my flesh and blood.

The truth came out when my ‘sister’ got a DNA kit for her birthday and my stepmum finally confessed that there had been another man about the time that my sister was conceived.

Since then my sister and I have been meeting up but things are getting intense. 

Last time I saw her she came out with it and told me she wanted sex and to be honest so do I. 

But this feels so wrong. On one level even though we aren’t related, she still feels like family. 

She now keeps calling me and I know in my heart I love her but is it right to take it further?

DEIDRE SAYS: She’s not a blood relative, nor did you look after her in a position of trust so you’re legally free to have a relationship or marry, but taking this further would no doubt impact the larger family.

Your family has thought of you as brother and sister for over three decades so it’s going to take a big mindset shift to see you as an established couple.