Farquhars of Lasswade

My Name is Alex. Farquhar,my ancestors were originally from Loanhead , and I have managed to find ancestors back to 1733, his name is Alexander Farquhar, this is where my problem comes in . Alexander was born to James Farquhar and Katherine Kinloch they were married about 1723 , easy so far now comes the mystery. Katherine was born in 1715 , and Iam unable to find James birth date so you can see where my problem lies Born 1715  married 1723 oops this is definitely her birth date as I have the copy of her birth certificate and it verifies her date of birth , I appreciate that there may be a mistake somewhere if only I could find it . I wouldbe very grateful for any help available