I assume you have a leased lines between two or multiple routers and wants to create multiple bundles..
First, two ways to bundle those links..Based on username and based on endpoint discriminator. Here is the link which explains which is the best in which condition..
http://cisco.com/warp/public/131/mppp_bundle_name.html
You can refer to the sample config below, but remove "miltilink-group x" command under the t1 intreface and configure "intreface virtual-template 1" instead on "interface multilink x"
http://www.cisco.com/univercd/cc/td/doc/product/aggr/10000/10ksw/mlppos.htm
I can try explain it here.
Now lets say router has 4 links and you want to create two bundles with two links in each, you use config like this to create two bundles, one for username abc and other for username xyz with two links in each bundle.
remote router
===========
int serial0
ppp chap host name abc
ppp multilink
int serial 1
ppp chap host name abc
ppp multilink
int serial2
ppp chap host name xyz
ppp multilink
int serial3
ppp chap host name xyz
ppp multilink
Central router
============
multilink virtual-template 1
multilink bundle-name authenticated endpoint
interfave virtual-template 1
ppp multilink
Make sure to include "ppp multilink" for all the serial interface on central router with other config.