Trying To Get - List Of Brokers With One Case Only In Last 9 Months

I have a problem where I need to return a list of Brokers that have had only one case and that case was in the last nine months, the script below was returning appropriate numbers until I amended it to add the date of that case (cdateReceived) and the related join.

There were 470 rows returned before the addition of the cdateReceived and 1780 rows after. Ordinarily you would expect the dataset to grow with the addition of a join on a one-to-many realtionship but the criteria should be limiting the resuilts to be brokers with only one case!!! It should not then increase the number of rows.

What am I mis-understanding?

SELECT TOP 100 PERCENT
dbo.brokerDetails.bFirstname + ' ' + dbo.brokerDetails.bSurname AS Broker,
dbo.brokerCompany.companyName,
dbo.brokerCompany.cTown,
dbo.brokerCompany.cPostCode,
ISNULL(dbo.brokerParent.pName, 'DIRECTLY AUTHORISED') AS Network,
dbo.cases.cDateReceived

FROM dbo.brokerDetails INNER JOIN
dbo.brokerCompany ON dbo.brokerDetails.bCompany = dbo.brokerCompany.companyID LEFT OUTER JOIN
dbo.brokerParent ON dbo.brokerCompany.cNetworkID = dbo.brokerParent.parentID INNER JOIN
dbo.cases ON dbo.brokerDetails.BrokerID = dbo.cases.BrokerID
WHERE (dbo.brokerDetails.brokerID IN
(SELECT TOP 100 PERCENT brokerID
FROM dbo.cases
WHERE (cDateReceived < DATEADD(mm, - 9, GETDATE())) AND (Spiked = 0) AND (IsDirect = 0)

GROUP BY brokerID
ORDER BY brokerID
)
)
AND (dbo.brokerDetails.brokerID IN
(SELECT TOP 100 PERCENT brokerID
FROM dbo.cases
WHERE (spiked <> 1) AND (IsDirect = 0)
GROUP BY brokerID
HAVING count(caseID) =1
ORDER BY brokerID
)
)
ORDER BY dbo.brokerDetails.bFirstname + ' ' + dbo.brokerDetails.bSurname