[SalesForce] Query parameter checking for related list size

You have to write a visualforce page for the Contact standard page layout, add it to the layout and write an extension:

Visualforce Page:

<apex:page standardController="Contact" extensions="MyExtension">
    <apex:pageBlock title="{!$ObjectType.Contact.labelPlural}">
        <apex:pageBlockTable value="{!Contacts}" var="cont">
            <apex:column value="{!cont.Name}" />
        </apex:pageBlockTable>
    </apex:pageBlock>
<apex:page>

Controller extension:

public class MyExtension {
    private final Contact cont;

    // Getting the current contact
    public MyExtension(ApexPages.StandardController stdController) {
        this.cont = (Contact)stdController.getRecord();
    }

    // Getting related contacts based on the Account-ID excluding the current contact
    public List<Contact> getContacts() {
        return [SELECT Id, Name, AccountId
                FROM Contact 
                WHERE AccountId = : cont.AccountId)
                AND Id != cont.Id]
    }
}

See the blog for SOQL subquery

You can use a inner query to achive this.

Try this code:

List<Account> accountList = [Select Id, Name,(Select id from AccountContactRoles), (Select Id from Contacts)   from Account where Id=: 'some id'];

System.debug('###'+accountList);

for(Account obj : accountList){
    System.debug(':::'+obj.Contacts);
    System.debug(':::'+obj.AccountContactRoles);
}