我家人 (my family)

我家有五个人 : 妈妈，爸爸，两个姐姐和我。 Grammatically correct but not according to cultural preference. So one look and is not written by a native... This is understandable.  You are at the beginning stage.  More importantly, it is understandable.  Here's a more elegant version...

我家五口人, 双亲, or 父母 姐姐两个和我.  两个姐姐和我 is the more common form.
There are five people in my family: : my mother, my father, my two older sisters and me.

我家 (my family)
我的家庭 
我家 means "my home" 

我家有五个人 : 妈妈，爸爸，两个姐姐和我。
我家有五个成员，爸爸妈妈，两个姐姐和我。
There are five members in my family : father, mother, two older sisters and me.

我家 (my family)

我家有五口人 : 妈妈，爸爸，两个姐姐和我。

<em>*口 kou3</em>

Reason is that, Kou口 is the measure word for family members; 

                      Ge个 is the measure word for general case. I.E., one person, 一个人； one classmates一个同学Tong Xue

                     another measure word for people, is 位 (wei4). It is used in polite situations. I.E., 一位老师，One teacher ；这位领导 "This leader"

我的家

我家有五口人 ： 爸爸、妈妈、两个姐姐和我。

I personally think it should be 爸爸妈妈 in Chinese, otherwise it will be odd to me saying "我的妈妈爸爸" or "我妈爸". 

爸妈，爸爸妈妈

我家 (my family)

我家有五个人 : 妈妈，爸爸，两个姐姐和我。
There are five people in my family : my mother, my father, my two older sisters and me.

It is perfect,no need to modify, you are right,爸爸 usually used befor 妈妈，but when 爸爸 marry into and live with 妈妈' family, you should say 妈妈and 爸爸。

Besides,I think you say 我 before 两个姐姐is better, 1112 is better then 1121