Performing COUNT() on a computed Column from a VIEW - sql-server

Question

So all I want to do is have a view that shows how many kid between and including the age of 5 - 18 are in each family. I AM USING SQL SERVER.
The view I Have written to get the Family Members Ages is
CREATE VIEW VActiveMembers
AS
SELECT
TM.intMemberID AS intMemberID,
TM.strFirstName AS strFirstName,
TM.strLastName AS strLastName,
TM.strEmailAddress AS strEmailAddress,
TM.dtmDateOfBirth AS dtmDateOfBirth,
FLOOR(DATEDIFF(DAY, dtmDateOfBirth, GETDATE()) / 365.25) AS intMemberAge
FROM
TMembers AS TM
WHERE
TM.intStatusFlagID = 1
intStatusFlag = 1 is just a flag that means the member is active.
Now I have tried for about 3ish hours to figure this out but I cannot figure it out. Here is the one where instead of trying to get the solution in one fowl swoop I tried to step wise it, but then I still didn't get the result I wanted.
As you can see I didn't use the view where I calculated the AGE from because the "Multi-part Identifier could not be bound" I have seen that error but I couldn't get it to go away in this case. Ideally I would like the count to be performed on the VIEW instead of recalculating the ages all over again
CREATE VIEW VActiveFamilyMembersK12Count
AS
SELECT
TF.intParishFamilyID,
COUNT(DATEDIFF(DAY, dtmDateOfBirth, GETDATE()) / 365) AS intMemberAgeCount
FROM
TFamilies AS TF
INNER JOIN
TFamilyMembers AS TFM
INNER JOIN
VActiveMembers AS vAM ON (TFM.intMemberID = vAM.intMemberID)
ON (TFM.intParishFamilyID = TF.intParishFamilyID)
WHERE
TF.intStatusFlagID = 1
GROUP BY
TF.intParishFamilyID
I wanted to just get a count using the age calculation just to see If I could get a correct count of members in a family, then I could start building upon that to get a count of members of a certain age. The result I get back is 2 but there are guaranteed 3 members to each family.
The result I am looking For is this
Family_ID | K12Count
-----------------------------
1001 | 2
1002 | 0
1003 | 1
1004 | 0
Here is a list of resources I looked up trying to figure this out, maybe one of them is in fact the answer and I just don't see it, but I am at a loss at the moment.
SQL Select Count from below a certain age
How to get count of people based on age groups using SQL query in Oracle database?
Count number of user in a certain age's range base on date of birth
Conditional Count on a field
http://timmurphy.org/2010/10/10/conditional-count-in-sql/
*** EDIT ***
CREATE VIEW VActiveFamilyMembersK12Count
AS
SELECT
TF.intParishFamilyID,
SUM(CASE WHEN intMemberAge >= 5 AND intMemberAge <= 18 THEN 1 ELSE 0 END) AS intK12Count
FROM
TFamilies AS TF
INNER JOIN TFamilyMembers AS TFM
INNER JOIN VActiveMembers AS vAM
ON (TFM.intMemberID = vAM.intMemberID)
ON (TFM.intParishFamilyID = TF.intParishFamilyID)
WHERE
TF. intStatusFlagID = 1
GROUP BY
TF.intParishFamilyID
GO
THIS IS THE SOLUTION ABOVE.

Answer 1

Conditional count is the way to go.
Something like:
SELECT intParishFamilyID,
COUNT(CASE WHEN intMemberAge >=5 and intMemberAge <=18 THEN 1 ELSE 0 END)
FROM
TFamilies AS TF
INNER JOIN TFamilyMembers AS TFM
INNER JOIN VActiveMembers AS vAM
ON (TFM.intMemberID = vAM.intMemberID)
ON (TFM.intParishFamilyID = TF.intParishFamilyID)
WHERE
TF. intStatusFlagID = 1
GROUP BY
TF.intParishFamilyID