Jealousy is a feeling which is quite common  between  the people of same age group .may be you are paying more attention on ur sis in law then your own  relationship as you might be noticing lots of pre wedding fun between the two right now but probably u might have to remind urself that there was a phase of excitement in ur wedding time also n don't worry if u 'll will focus about the good thing of ur relationship n how beautiful ur relationship is ur'll soon stop paying attention. Take care, dress up  n enjoy the wedding at home.☺