since this thread was brought up, i thought i might comment on this.
wouldnt her sister-in-law's husband be her brother... so, naturally, wouldnt you just write "my brother and his wife?"
just found it a little strange.
and where the heck is said pie chart? i was really curious. i am a visual learner.
It could be her husbands sister and her husband? So essentially her brother in law and sister in law