Looking at the horoscope of your sister, Jupiter is the lord of 7th house of marriage and married life and well placed in the 9th house. Venus the karka of marriage is debilitated in the 4th house. There is no Manglik dosha as Moon is cojoined with Mars in the 7th house. However Matching of the horoscope should be done for marital happiness. Strong chances of marriage are before March 2015. Can be in the second half of 2014 as well. Doing the following remedies will help get desired results.
1. Read Hanauman Chalisa Daily.
2. Keep fast on Thursdays.
Please note that the the Ashtkoot Guna Milan is 22.5 guna matching out of 36, where we consider 18 as minimum. There is 2/12 Bhakoot Dosha. The Boys horoscope is especially bad for marriage as he is Ashtam Manglik, that means that Mars is in the 8th house. Venus the Karka for marriage is debilitated in the Navamsha chart. Rahu is positioned in the 7th house.
For detailed Horoscope Matching & Effective Remedies you may look at the Paid Services, in which I tell you exactly what will be the influence of the planets in these houses and also do Rajju Matching and detailed Ashtkoot Guna Milan Analysis.