My 2 year niece weighs 30kgs (66.13 lbs) and tall for her age (3 feet/91cm tall). Despite her weight she does not really eat much.. we we're advised that it's growth spurt. Is there a cause for concern? Is this normal?
For weight, 30 kilograms is quite heavy for a 2 year old. Per the cdc growth charts1 @dave posted in comments, a two year old will typically be between 10 and 15 kilograms (20-35 pounds) (5%-95% range). However, you need to take into account her height in determining what you'd expect her to weigh; for that you have weight-for-stature (weight-for-height) charts.
Based on the height you reported (3' or 91cm), the range is slightly higher (as she is indeed tall for her age); the typical range (5%-95%) is between 12 and 16 kilograms. 30 kilograms is off the linked chart; you'd expect a 30kg child to be more like 4' tall (125cm) or more.
So - no, it's not "normal", based on the statistics. Whether it's healthy is something the pediatrician would address. If they're not concerned, then perhaps it's worth asking why? Perhaps the measurements were provided incorrectly - maybe she's really 30 pounds for example, and her parents misheard/misunderstood the doctor. If she seems substantially heavier than other children her age (30kg would be substantially heavier), and it's something that's worrying her parents, it's definitely something worth asking about - if nothing else just to find out why the pediatrician isn't worried.
 CDC growth charts are based on American children; WHO growth charts may show somewhat different results, although usually in the same ballpark. Unfortunately they're much harder to read, so we tend to use CDC charts here. For reference, the weight-for-height for girls in WHO shows slightly higher (5% or so) estimates than the CDC does, but not enough to change the details significantly above.