Multiple missing characteristics - Using egen to count number of members in household

I wish to count the number of members in a household for the given survey data.

hh_id	memgndr_1	memage_1	memrshp_1	memgndr_2	memage_2	memrshp_2	memgndr_3	memage_3	memrshp_3
101	Male	25	Head		45		Male	78	Father
102		36		Female		Sister
103	Female	28	Sister	Male			Female		Mother
104			Sister		67	Mother
105	Male	48		Female

As apparent from the above table, for each member, the characteristics (gender, age and relationship to household head) may have missing values. In such a case, how do I use egen command to calculate the number of members in a household such that a member gets counted in the total even if one characteristic has a valid value for that member.